Metal silicide formation is a process widely used in many metal-oxide semiconductor (MOS) device fabrication process flows. By way of example only, metal silicide is commonly used to form device contacts. Advantageously, metal silicide contacts can be formed using a maskless process thus simplifying production and reducing costs. Namely, a metal (such as nickel (Ni)) is deposited onto the device, and the metal silicide contact will form only in those areas where the metal is in contact with the silicon. Accordingly, contacts produced in this manner are termed “self-aligned” contacts.
However, conventional nickel (Ni) silicide formation below about 16 nanometers (nm) thickness (about 8 nm as deposited Ni) has shown yield degradation in every generation from 65 nm to 32 nm, due to thermal stability issues and pipe defect formation. See, for example, Imbert et al., “Nickel silicide encroachment formation and characterization,” Microelectronics Engineering, Volume 87, Issue 3, pgs. 245-248 (March 2010) and Yang et al., “Advanced in situ pre-Ni silicide (Siconi) cleaning at 65 nm to resolve defects in NiSix modules,” Journal of Vacuum Science & Technology B, Volume 28, Issue 1 (2010), the contents of both of which are incorporated by reference herein.
Therefore, a solution is needed to extend Ni silicide to next CMOS generations which requires thinner and uniform (sub 15 nm) silicide contacts.